Our experiments thus far suggest that some factor or factors in the chick embryonic environment inhibit synthesis of UDP- glucuronyltransferase. We propose to answer the following questions (1) will phenobarbital overcome "embryonic inhibition" and prematurely induce transferase activity when injected into the air space or yolk sac; (2) will phenobarbital induce proliferation of ER in embryo liver cells in ova, as it does during culture.